CHAPTER XXIII 



THE EYE AND SOME COMMON AFFECTIONS 



The horse, like all other animals, is Uable to suffer from 

 various diseases and injuries of the eyes, some of which 

 may render it either partially or completely blind. 

 Perfect vision, although not essential for work, is an 

 indispensable feature in relationship to soundness, so 

 that the most venial affection of the eye does, in this 

 animal, materially detract from its commercial value. 



A horse may be perfectly blind, yet to a casual observer 

 the eyes may appear quite normal. There are some 

 affections implicating the eyehds only ; others the globe 

 of the eye ; the glands in connection with the eyelid and 

 eye, and, in many instances, the whole of the structures 

 in connection with the eyelids and eye become, more or 

 less, implicated. 



The eyes occupy a somev/hat sheltered position and are 

 protected and shaded by the eyelids and eyelashes ; 

 nevertheless, in spite of this, foreign bodies, such as a 

 particle of chaff, etc., frequently become lodged on the 

 transparent surface of the eye, setting up a variable 

 degree of inflammatory action. 



The eyelids are lined by mucous membrane, and as this 

 is a highly vascular structure it follows that an injury to 

 the eyelid, or anything which causes irritation is ex- 

 tremely liable to be followed by inflammation. 



In addition to the shelter afforded by the eyelids, 

 each eye is lodged in a complete bony cavity, the eyeball 

 itself being pierced at the back by a large nerve — the 

 optic nerve, which is derived from the base of the brain, 

 where the right and left optic nerves cross, and constituting 



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